InSb-based quantum dots grown by metal-organic vapor-phase epitaxy (MOVPE) on InAs substrates are studied for use as the active material in interband photon detectors. Long-wavelength infrared (LWIR) photoluminescence is demonstrated with peak emission at 8.5 µm and photoresponse, interpreted to originate from type-II interband transitions in a p-i-n photodiode, was measured up to 6 µm, both at 80 K. The possibilities and benefits of operation in the LWIR range (8-12 µm) are discussed and the results suggest that InSb-based quantum dot structures can be suitable candidates for photon detection in the LWIR regime.
We have demonstrated surface normal detecting/filtering/emitting multiple functional ultraviolet (UV) optoelectronic devices based on InGaN/GaN, InGaN/AlGaN and Al x Ga 1-x N/Al y Ga 1-y N multiple quantum well (MQW) structures with operation wavelengths ranging from 270 nm to 450 nm. Utilizing MQW structure as device active layer offers a flexibility to tune its long cut-off wavelength in a wide UV range from solar-blind to visible by adjusting the well width, well composition and barrier height. Similarly, its short cut-off wavelength can be adjusted by using a GaN or AlGaN block layer on a sapphire substrate when the device is illuminated from its backside, which further provides an optical filtering effect. When a current injects into the device under forward bias the device acts as an UV light emitter, whereas the device performs as a typical photodetector under reverse biases. With applying an alternating external bias the device might be used as electroabsorption modulator due to quantum confined Stark effect. In present work fabricated devices have been characterized by transmission/absorption spectra, photoresponsivity, electroluminescence, and photoluminescence measurements under various forward and reverse biases. The piezoelectric effect, alloy broadening and Stokes shift between the emission and absorption spectra in different InGaN-and AlGaN-based QW structures have been investigated and compared. Possibilities of monolithic or hybrid integration using such multiple functional devices for biological warfare agents sensing application have also be discussed.
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